Radio buttons/checkboxes in QWebView broken if using stylesheet in a QTabWidget

When using QWebView inside a QTabWidget and setting any stylesheet on the QTabWidget, checkboxes and radio buttons on websites act weird.

I don't write C++, but this PyQt code reproduces the behaviour:

import sys

from PyQt5.QtCore import QUrl
from PyQt5.QtWidgets import QApplication, QTabWidget
from PyQt5.QtWebKitWidgets import QWebView

app = QApplication(sys.argv)
tabwidget = QTabWidget()
tabwidget.setStyleSheet("""
    QTabBar::tab {
        color: red;
    }
""")
webview = QWebView()
webview.load(QUrl("http://www.echoecho.com/htmlforms10.htm"))
tabwidget.addTab(webview, "test")
tabwidget.show()
app.exec_()

The attached video shows what I mean. (I hope it is attached - the check box is rendered as unchecked).

It does not happen when not setting a stylesheet, and doesn't happen on Archlinux (so QWebKit + Stylesheet style + Windows style?). I also couldn't reproduce it in a quick test with a QGroupBox and QRadioButtons.